Under certain conditions, gas can accumulate in the interior of a battery. If there is no way for this gas to escape from the battery housing, pressure build-up may eventually cause the battery to explode.
Various vents have been employed to allow gas to escape from a battery at a predetermined burst pressure. Vent designs include openings that are normally sealed with valves, diaphragms and gaskets. It is important that the vent be sealed from the ambient atmosphere until the burst pressure is reached, to prevent ingress of water, air and other contaminants into the battery.
Some types of batteries include a coined area in the housing that has a reduced wall thickness designed to burst when a predetermined pressure is reached within the battery housing. However, this vent design is difficult to implement in batteries where venting must occur at relatively low pressures at which the shear stress is insufficient to break the thinned wall. Moreover, it may be problematic to precisely control wall thickness using a coining process.